• by Laurie Sullivan , Staff Writer @lauriesullivan, September 25, 2014

The top five advertisers, in aggregate, spent about $20 million on mobile device keywords to run Google product listing ads from April to June, 2014, per a study released Wednesday.

Adgooroo studied 327 advertisers. AT&T spent $5.8 million to generate 32.8 million impressions, generating 2 million clicks at an average click-through rate of 6.26% at an average cost per click of $2.83, with about 256 ads running.

Sprint followed at No. 2, spending $5.4 million to generate nearly 31.5 million impressions, and generating about 1.9 clicks at a 5.99% average CTR at a cost of about $2.89 with about 170 ads running. Best Buy followed with $5.2 million, 38.6 million impressions, 2.3 million clicks at an average CTR of 6.20% and average CPC of $2.17. Walmart spent $2 million; and Verizon Wireless, $1.8 million.

Best Buy had far more ads running, at about 1,178 -- compared with the other four advertisers in the Top 5, which averaged 229 keywords each. Only two of the other 322 advertisers sponsored more ads than Best Buy: eBay at 2,228 and Rakuten at 1,224.

While the top three advertisers spent $5.5 million on Google PLAs for mobile device keywords, the bottom three advertisers -- HSN, TigerDirect and BuyDig.com averaged just more than $79,000 each.

In total, Adgooroo found that 327 advertisers spent $26.4 million to sponsor the 339 mobile device-related keywords running between May and July, at an average CRT of 6.54% and an average CPC of $2.26. The keywords range from iphone 5s and iphone 5c to best tablet and Samsung galaxy s3.